Method and apparatus for completing wells



Sept. 29, 1959 w. H. GRIFFIN METHOD AND APPARATUS FOR COMPLETING WELLS 4Sheets-Sheet 1 Filed March 30, 1954 iii a W//ber H. G/lff/f? INVENTOR BYM a? 1 Arrok/vfim Sept. 29, 1959 w. H. GRIFFIN 2,906,339

METHOD AND APPARATUS FOR COMPLETING WELLS Filed March 50, 1954 4Sheets-Sheet 2 I 3 I I I I A I W//ber H. 6r/ff/fl INVENTOR.

ATTORNEYS Sept. 29, 1959 w. H. GRIFFIN 2,906,339

7 METHOD AND APPARATUS FOR COMPLETING WELLS Filed March 30, 1954 4Sheets-Sheet 3 W/ /b er H. 67/ ff/n INVENTOR.

Sept. 29, 1959 w. H. GRIFFIN 2,905,339

METHOD AND APPARATUS FOR COMPLETING WELLS Filed March 30, 1954 4Sheets-Sheet 4 W//ber H. Gl'fff/fl INVENTOR.

BY z w M f A TTOR/VEVS 2,906,339 Patented Sept. 29, 1959,

ice

METHOD AND APPARATUS FOR COIVIPLETING WELLS Wilber H. Griffin, Houston,Tex.

Application March 30, 1954, Serial No. 419,729

22 Claims. (Cl. 16635) This invention relates to the completion ofwells. In one of its aspects it relates to a new means and method forfiring a well perforator. In another of its aspects it relates to adetonator or actuator to be lowered or dropped into a well and firethrough a stop to fire a perforator, pierce a closure, etc. In stillanother of its aspects it relates to a new method of well completion.

Heretofore, Well perforating guns have included in one assembly both theperforating means and the apparatus for firing the gun. This arrangementgives rise to the problem of premature and unintentional firing of thegun both on the surface and in the hole. Various means have beenprovided to prevent accidental firing of the gun, but, notwithstandingthe most elaborate precautions, unintentional firing of the gunsheretofore used sometimes occurs.

Where the guns were mechanically fired they generally employed as a partof their firing mechanism conventional blank cartridges to set off theirprimer cords. These cartridges are loaded with a relatively unstableexplosive such as fulminate of mercury. These unstable explosives, inaddition to their instability, deteriorate in a short time under theelevated temperatures frequently encountered in present day deep wells,and when deteriorated sometimes fail to explode when desired. They alsosometimes fire prematurely When subjected to elevated temperatures overan extended period of time. These characteristics do not normallypresent any particular problem when the perforating gun is run in on awire line as the gun may be lowered into position in many instances inan hour or so. Where, however, it is desired to run the gun on the lowerend of a string of production tubing for purposes which will hereinafterappear, the gun will be in the well upward of ten or twelve hours inmany instances and some means needs to be provided to insure properoperation of the cartridges.

This invention contemplates the complete separation of the firingmechanism from the remainder of the gun until such time as the gun, lessthe firing mechanism, is in place in the well and it is desired to firethe gun. Thus, unintentional actuation of the gun by the firingmechanism is impossible. The firing mechanism will be in the well only ashort time before the gun is fired and, therefore, the temperature inthe well will not affect the firing mechanism. In the event misfire doesoccur, the firing mechanism can be retrieved with a wire line, reloaded,and run into the well again. Thus the gun, less the firing mechanism,can be run into the well without danger of having to pull the string toreload the firing mechanism.

When a well bore has been plugged and is ready for perforating it willusually be found that the bore is filled with a fluid such as drillingmud. The hydrostatic pressure exerted by this column of fluid at theformation may be greater than the pressure of the formation to beperforated. If the well is perforated with this .fluid in place, the mudwill tend to.flow into the formation through the perforations. Thus, itis frequently desirable to replace this fluid before perforating with alighter fluid which will exert a lesser pressure due to the hydrostatichead than the formation pressure. This procedure is highly desirable asthe well will begin to flow as soon as it is perforated and the fluid inthe Well' bore will not enter the formation in any appreciable amount(the firing of the gun is believed to carry some fluid into theperforations) and contamination of the formation will be held to aminimum. Where the formation pressure is not of a magnitude to permitthe procedure outlined above, it is customary to first perforate thewell and then induce flow by swabbing or the like to reduce pressureexerted by the hydrostatic head in the well. This, of course, permitscontamination of the formation by fluid in the well bore, as forinstance by mud plastering the perforations and the formation adjacentthereto, or where water is taken up by a bentonite formation causing thebentonite to swell, etc. Thus, it would be advantageous to have a methodof well completion wherein a formation whose pressure is less than thehydrostatic pressure of fluid in the bore adjacent the formation whenthe well is perforated may be induced to flow immediate ly uponperforation of the formation. Such a method would also be useful wherethe formation pressure is of greater magnitude than the pressure exertedby a light column of liquid.

In many instances, it would be advantageous to have the lower end of thetubing full open when the last operation is complete to permit laterwork-over operations through a full open tubing. It would further beadvantageous to be able to run a dry tubing into a Well and after thetubing is run to open it to fluids in the well bore using a simple andinexpensive method.

It is an object of this invention to provide a method and apparatus formechanically setting off an explosive charge in a well in whichaccidental firing of the explosive by the firing mechanism isimpossible.

Another object is to provide a method and apparatus for mechanicallysetting off an explosive charge in a well in which the explosive ispositioned in the well and the firing mechanism used to set off theexplosive is only introduced into the well after the explosive is inplace.

Another object is to provide a means and a method for mechanicallyfiring a perforating gun in which accidental firing of the gun by thefiring mechanism is impossible.

Another object is to provide a mechanically fired perforating gun whichmay be run into a well on the lower end of a production string withoutdanger of misfiring due to deterioration of the firing mechanism by welltemperatures.

Another object is to provide a perforating gun in which the gun, lessthe firing mechanism, is first positioned in the well, and then thefiring mechanism is introduced into the well and fires the gun.

Another object is to provide a perforating gun adapted to be run on aproduction string of tubing, which upon firing falls to the bottom ofthe hole as debris, leaving the bore of the production stringunobstructed to permit work-over operations through the productionstring.

Another object is to provide a go-devil actuator for perforating guns orlike apparatus in which the go-devil fires a shaped charge into the gunor other apparatus to actuate same.

Another object is to provide a method and apparatus for completing wellsin which the hydrostatic pressure exerted by the fluid in the well boreadjacent the formation to be produced is substantially reduced at thesame time that the formation is perforated insuring immediate flow ofthe formation fluid into the well bore and preventing contamination ofthe formation by the fluid in the well bore.

Another object is to provide a method and apparatus for'completing'wellsin Which the pressure of the formatiori'to' be produced is relativelylow and in'which the" hydrostatic pressure exerted by the fluid in thewell bore adjacent the formation to be produced is reduced at theinstantoffiring the perforating gun to a value imme diatefiow oftheformation'fluid into thewell bore;

Another object is to provide a method and apparatus for permanentlycompleting wells in which the produc-" tion tubing is full open when thewell is brought in.

Another object is to provide a simple and inexpensive means of removinga closure from the lower end of a string'o'f tubing in a well.

Another object is to provide a new'method of loading a primer'cord in aflexible sheathing.v

Other objects, advantages and features of this invention'w'illbea'pparent to one skilled in the art upon" a consideration ofthewritten specification, the appended claims, a'n'dthe attacheddrawings.

In the drawings wherein there is shown by way of example anillustrative" embodiment of this invention, and wherein like referencenumerals indicate like parts:

Fig. 1 is a view in vertical section through a well casinglsh'owing' invertical elevation-a perforating gun embodying this invention positionedopposite the formation 7 to be penetrated with a'portion' of the tubingcut away to' show the go-devil actuator falling through the tubing;

Fig. 2 is a view in vertical elevation of a preferred form ofg'o-devilactuator;

Fig. 3 is a view on an enlarged scale of the charge carrier and fittingthereabove taken along the line 3-3 of Figl-l with parts broken away toillustrate certain details, and showing the go-devil actuator of Fig. 2in firingiposition in dotted lines;

Fig. 4 is a view along the line 4-4 of Fig. 3;

Fig. 5 is aview along the line 55 of Fig. 3;

Fig. 6 is a view along the line 66 of Fig. 3;

Fig. 7 is a view along. the line 77 of Fig. 2;

Fig. 8 is a cross-sectional view through the go-devil actuator takenalong the line 88 of Fig. 7;

Fig. 9 is a fragmentary view of a modified form of go-devil actuator;

Fig. 10 is a sectional view through the device utilized in loadingprimer cord in aflexible sheathing;

Fig. 11 is a view in vertical section through a well after theperforating gun has been fired with the tubing. and a modified form ofconnector fitting shown-in elevation, showing the casing perforated andthe fragments of the charge carrier of the gun, which shattered Whenfired, on the bottom ofthewell;

Fig. 12 is a view along the line'12-12-of Fig. 11

Fig. 13 is a fragmentary view of the lowermost length of a well tubingillustrating in dotted outline a brittle fitting for attaching the gunto the tubing which shattered and fell to the bottom ofthe well asdebris When the gun was fired, leaving the production string open topermit work-over operations. This figure also illustrates the use of animperforate string of tubing and fitting used when the gun isrun on adry string of tubing, wherein the fitting was shattered to open thetubing to well fluids at the same time that the gun was fired to reducethe pressure in the Well bore adjacent the formation to be produced atthe time of firing of the gun; and

Fig. 14 is a view in vertical section through a modified form of fittingfor attaching the gun to the production string. and illustrating the useof a booster asa part of the primer cord.

The perforating gun illustrated includesa' more or less conventionalcarrier loaded with shaped charges. A-

primer cord extends from charge tocharge and has a portion of its lengthpositioned at the top of the carrier and in general axial alignment withthe tubing from which the carrier is suspended. Such primer cord-is aflexible cord-type explosive or detonator fuse, well known for this use,such as the well known Primacord manufactured by the Ensign-Bickford.Company, of Simsbury,

4 Connecticut. Usually it is a hollow fabric or plastic tube filled witha' well known detonable explosive such as'penta--erythritoltetranitrate. It may be fired by applying a detonating shockat any point of its length. A go-devil actuator, which may be droppedfrom the surface after the carrier is in place, carries the firingmechanism for the gun. The firing mechanism is inertia operated and isactuated by the go-devil landing'upon the fitting by which thecharge'ca'rri'er is secured" to the tubing. The firing mechanism setsoff a shaped'charge in the nose of the go- 'devil which in turn ignitesthe primer cord. While the actuator illustratedi'sago dev'il, it will'beappreciated by those skilled in" the art that the actuator might be runinto the well and fired in other ways which will suggest themselves topersons skilled in'the' art. There may also be provided a booster forthe primer cord which is positioned in the fitting in the line of fireof the shaped charge in the go-devil actuator so that the actuator uponfiring will ignite theb'ooster, which in turn insures that the primercord will be fired.

Referring now to the drawings and in particular to Fig. 1, there isshown a casing'lS in a well bore anda tubing 16 in the casing. Thelowermost section 16a of tubing 16:

is perforated to provide ingress into the tubing while producing theWelland to permit fluid in the well such as drilling mud to be removedby introducing water or oil or'other-fiuids which would be less harmfulto the formation. Replacing the well fluid with alighter fiuid willprevent the perforated formation from being partially orcompletely'blocked or contaminated by the mud or other fluid due" to ahigher pressure fiuid in the bore than the formationpressure' of theformation penetrated which wouldca'use well fluid to' flow into theformation, and due to a deleterious fiuid being carried into theformation by the bullet or force jet which penetrates the formation.Such U-tubing is preferably carried out with the perforate section oftubing 16a at or below the formation tobe penetrated to remove the fluidfrom the well bore opposite such formation.

A collar locator 17 is slidably received about perforated sections 16aand assist in-positioning the gun at the desired depth in the usualmanner as will be readily understood by those skilled in the art.

The portion of the perforating gun which is run into the well ontubingifi includes a charge carrier 18 secured to the lower end oftubing 16 by a fitting 19. The fitting 19 may be considered as a part ofa perforating gun and provides a stop part for arrestingdownwardmovement of; the go-devil shown in Fig. 2. The carrier 18 is loadedprimer cord2il will be used as willbe understood by thoseskilled in theart. I I

The go-devil 21 illustrated in Fig. 2 includes anexplosive charge,preferably a downwardly firingshaped charge, in its nose. Thego-devilmay be made up with one ormore weight sections 21a; asillustratedto provide the necessary weight to rapidly carry it to'thebo-ttom'of the hole.-

The method of use of the perforating gun is as follows: The chargecarrier 18 isrun into the well on tubing 16 and located atthe desireddepth so as to be'opposite the formation to be penetrated; The tubingmay he landed, the'well head connections completed and the heavy mudU-tubed out of the hole ifdesired. The go-devil 21 is then droppedthrough the tubing 16 until the explosive charge in its nose is fired bythe go-devil striking the stop.

part in fitting'19 with .sufiicient force to operate the inertiaoperated firing mechanism which sets off the charge, which in turn firesthe gun by igniting the primer cord. While it is preferred to use ago-devil which is dropped from the surface, it will be understood thatthe go-devil might be lowered into the well on a wire line or that thecharge might be lowered into the well and fired by other means.

At the time the well is perforated, all of the well head apparatususually employed in flowing the well is in place. The go-devil will takeseveral minutes to reach the bottom of the hole and all valves in thechristmas tree may be in normal producing position when the well comesin to insure maximum control. Upon firing of the gun the carrier 18 willshatter and fall to the bottom of the hole in fragments as illustratedin Fig. 11. Formation fluids may then enter unobstructed through theperforations made by the gun and will enter the tubing through itsperforate section. The go-devil may be fished from the tubing at a latertime or may be left in the hole as desired.

It not infrequently occurs that the formation pressure of the formationto be penetrated will be less than the pressure within the cased wellbore adjacent the formation due to the hydrostatic head of fluid in thewell even though the well be filled with a light, unweighted fluid suchas water. If the well is perforated while subjected to this hydro-statichead, the fluid in the well will enter and perhaps contaminate theformation. This may be avoided by running a perforating gun on animperforate dry string of tubing closed at its lower end by animperforate fitting, that is, a fitting which closes the end of thetubing to entry of fluid, and opening the tubing to well fluid adjacentthe formation at the same instant that the formation is perforated. Themethod of accomplishing this is as follows:

The perforating gun is run into the well on an imperforate through thetubing and opening the tubing and firing the gun simultaneously bysetting off a shaped charge in the nose of the go-devil when it lands onfitting 19. The force jet from the shaped charge perforates the fittingto permit ingress of fluid into the tubing and at the same time ignitesthe primer cord. As the pressure Within the tubing will be substantiallyatmospheric, the pressure in the Well bore at the formation to beproduced will be much less than the formation pressure upon opening ofthe tubing, and flow from the formation into the well bore will beginimmediately upon perforation of the Well and the formation will not becontaminated by fluid in the well bore.

The apparatus employed in the above set forth method might be the sameas heretofore described with but slight modification. The tubing should,of course, be imperforate to exclude Well fluid from its bore andfitting 19 would also be imperforate for the same reason. The shapedcharge in the nose of the go-devil 21 would be fired adjacent thefitting 19 and the shaped charge would burn through the fitting 19 andfire the perforating gun. The hole burned through the fitting wouldpermit entry of well fluid into the tubing at the same time that the gunis fired. If desired, a brittle fitting 19 may be employed which willshatter into fragments upon firing of go-devil 21 leaving a full opentubing.

If desired, tubing 16 might be partially filled with liquid to preventputting too great a strain on the formation due to the sudden reductionof pressure in the well bore.

When the above method of well completion is employed, the fluid in thewell cannot be replaced with lighter fluid as is possible when theperforating gun is run on a perforate section of tubing. Thus, if it isdesired to replace the fluid in the well bore with some other ofallowing fluid'to circulate through fitting 19 while un- 6 fluid, thisshould be done before the perforating gun is run in.

It will also be understood that a closed string of tubing might be runat other times and for other purposes, and opened to well fluid withgo-devil 21, and such is contemplated by this invention.

Referring now to the details of the perforating gun illustrated andparticularly to Fig. 3, the fitting 19 which secures the charge carrierto the string of tubing has a bore 22 in its end adapted to be securedto the production string 16. A downwardly and inwardly sloping wallsection 23 of the bore guides the godevil 21, shown in dotted outline,into a reduced diameter portion of bore 22. The reduced bore sectionterminates in a stop 24 which arrests downward movement of the go-devil.Stop 24 is provided with a central bore 24a for the purpose desirablefluid is being dumped from the well. This will prevent any accumulationof solid particles in the fitting which might cushion the fall of thego-devil and prevent it from striking stop 24 with suflicient impact tooperate the firing mechanism of the go-devil. This hole also acts moreor less as a flame chamber and permits the shock wave and flame from theexplosive in the nose of the go-devil to easily reach the portion of theprimer cord 20 which is positioned therebelow. As will be illustrated ina modified form of fitting, it is not necessary to provide bore Z lainfitting 19 when a shaped charge is used as the charge will penetrate astop such as 24 and ignite a primer cord therebelow.

The carrier 18 for the shaped charges is threadedly secured to the lowerend of fitting 19 and provides a means for mounting the charges in theusual manner. Carrier 18 is a more or less skeleton frame made of abrittle material such as cast iron which will shatter upon firing of thegun and is made up in sections to permit the gun to have any desirednumber of shaped charges. Carrier 18 may be a hollow tube type carrierloaded with shaped charges which do not shatter if desired, but theexpendable carrier is preferred.

The manner of securing the several sections of the charge carriertogether is illustrated in Fig. 5. Each section of the charge carrier 18is provided at one end with a male part 18a and at the other end with afemale part 18b. The male and female parts of adjacent sections of thecharge carrier are pinned together by a bolt and nut 25. It will benoted that clearance is provided between parts 18a and 18b which willpermit slight misalignment of the several sections of the carrier as itis run into the hole, if necessary.

Shaped charges 26 are locked in place in the charge receptacles ofcarrier 18 by set screws 27. The charge receptacles of carrier 18 arespiraled about the carrier at intervals to provide perforations spacedabout and along the well bore as will be well understood by thoseskilled in the art.

A primer cord 29 extends from charge to charge and has a portion 20a ofits length arranged in axial alignment with the bore of the tubing fromwhich the carrier is suspended by wrapping the cord about the top shapedcharge several times. This top shaped charge will be fired by the jetfrom the go-devil and thus will act as a booster and insure firing ofthe primer cord. One end of the primer cord is secured to the carrier bythe uppermost bolt and nut 25 as indicated in Fig. 3 and the other endof the primer cord is inserted into a guide 28 on the lower end of thecharge carrier. The primer cord should be protected from well fluid andfor this purpose it may be encased within a flexible sheathing 2011 suchas synthetic rubber or the like.

In Fig. 6 there is illustrated a means for closing the open end ofsheathing Ztla to well fluids. The sheathing 2% is extended beyond theend of the primer cord a short distance. A rubber stopper 29 ofsubstantially the same diameter as the inner diameter of sheathing 20asubstantially greater diameter than the inner diarneter of sheathing isinserted into the end of the sheathing with its small diameter endforemost. The stopper .is positioned in engagement with the end of core2% so as to form substantially an extension thereof. The open end ofsheathing a is inserted into a short tube of malleable metal 31 such ascopper or the like which is then flattened 'or crimped to hold thestopper in place. The pressure of well fluid exerted against thesheathing 26a about the rubber stopper will prevent passage of wellfluids between the stopper and the sheathing 26a and keep the primercord dry.

Referring to Fig. 7, there is shown a preferred form of go-devil .forfiring the perforating gun. The explosive used is preferably a shapedcharge 32 positioned in the nose of go-devil 21 and arranged to firedownwardly and axially of go devil 21 when set off by the inertiaoperated hammer 33. The lower end of go-devil 21 is provided with ahousing 34 having a bore 35 and a counter bore 36. The upper end ofhousing 34 is threadedly secured to the weight bars 21a of the go-devilby -a threaded connection 37. The other end of the housing is closed bya plug 38. Nose plug 38 is rounded at 38a to prevent premature firing ofthe go-devil as it travels through the tubing. Plug 38 has an axial bore39 through which the jet from the shaped charge passes when the shapedcharge is fired. The bore is closed to exclude fluid by 'a transversewall such as plug 40 which is burned out by the jet when the shapedcharge is fired.

An elongate, tubular member 41 is positioned in bore 36. Tubular member41is provided at one end withan axial recess or bore 42 which partiallyreceives shaped charge 32, and at its other end with a plurality ofbores 43 which receive rim-firing blank cartridges 44. A flame chamber45 leads from bore 43 to bore 42. A length of primer cord 46 extendsfrom flame chamber 45to theshaped charge 32 and has one end insertedinto the rear of shaped charge 32 and held therein by several wraps oftape 47. A short section of tubing id is received over the other end ofprimer cord 46 and a blasting cap 49 is positioned in the section offlexible tubing with one end of the blasting cap directly adjacent thefree end of primer cord 46. This blasting cap may be er any commonvariety employing a relatively unstable explosive such as fulminate ofmercury. As illustrated in .Fig. 7, the blasting cap will be positionedjust below the ends of blank cartridges 44 and will be ignited by firingof blank cartridges 44. The blasting cap in turn will ignite the primercord 46 which will set off shaped charge 32. a

"The inertia responsive firing mechanism includes a hammer 33 which isslidably mounted in slide chamber or bore 35 and spring-loaded away frommember 41 by spring 50. Slide chamber 35 terminates at each end inabutment walls one of which is provided by tubular member 41 and theother by the weight member to which housing 34 is secured. Hammer 33 isprovided with a reduced diameter portion 334: which serves as a firingpin to fire rim-fire cartridges 44 upon actuation of the hammer. Blankcartridges 44 are arranged equidistant from the central axis of'housing34 and a portion of the rim of each cartridge lies under firing pin 33a.An intermediate reduced diameter portion 3311 between the firing pin 33aand the .large diameter portion of the ham mer provides a shoulder 330against which spring 5% is seated. The intermediate diamet r portion ofthe harnmer 33b also provides a guide for spring 56. The other end 56aof spring 5%) is seated against the adjacent end of member 41. When theactuator is assembled spring 50 urges hammer'33 away from rim-firecartridges 44.

In operation the'harnmer 33 will move toward blank cartridges 44 against'the force of spring 53 when the downward movement of .go-devil 21 isabruptly arrested by .the .go-devil striking stop 24. When this occursfiring pin 33a will strike and fire rim-fire cartridges 44 which in turnwill set off blasting cap 49. As noted above,

the blasting cap 49' will fire primer cord 46 which in turn will fireshaped charge 32. The force jet and flame from shaped charge 32 willtravel downwardly throughbore 24a in fitting 19 and set off primer cord20 to fire the perforating gun. There is but very slight clearancebetween housing 34 and member 41 and when shaped charge 32 is set oilthe blast will sufficiently distort the housing and member to retainmember 41 in the godevil even though plug 38 is severed from thego-devil.

In Fig. 9 there is shown a slightly modified form of the firingmechanism. Hammer 51 which corresponds to hammer'33 in the Fig. 7embodiment is provided at its uppermost 'end with a cartridge receivingbore 52. A rim-fire cartridge 53 is received in bore 52 with a portionof its rim directly below a projection or firing pin 54; With thisarrangement firing of the go-devil actuator will occur when hammer 51 ismoved downwardly any appreciable distance even though it does not strikerimfire cartridges 44 as upon the return of the hammer by spring 50firing pin 54 will fire cartridge 53 which will move the hammer towardcartridges 44 with sufficient force to overcome the spring 50 and firecartridges 44.

The explosives contained within blasting cap 49 and within blankcartridges 44 and 53 will not be affected by temperature conditionswithin the well as go-devil 21 will not be dropped into the-well untilthe operator is ready to fire the perforator. V I

Referring now to Figs. 11, 12 and 14, there is shown a modified form offitting for connecting the charge carrier to the well tubing. This formof fitting is preferred as it permits the use of a booster as a part ofthe primer cord whose explosive can be positively and permanentlyprotected from well fluids without difiiculty.

Fitting 55 secures the charge carrier to the string of tubing in thesame manner as does fitting 19. The fitting is likewise provided with atapering side wall 56 to guide the go-devil to the stop member 57 andcause the godevil to be substantially centered in the bore of thefitting when it strikes stop 57. The fitting differs from fitting 19 inthat the circulating port Zea has been replaced by a plurality ofcirculating ports 58 and in that the stop part 57 is imperforate. Thelower portion of the fitting is provided with a bore 59, a reduceddiameter bore 6%, and a further reduced diameter and threaded bore 61. Abooster 62 is received in these bores in the lower portion of thefitting. Booster 62 has a small diameter threaded portion 63 which isthreadedly received in bore 61 and a slightly larger diameter portion 64which is received in bore 60. Portion 6 of the booster is provided withan annular groove in which is positioned an O-ring 65 to prevent passageof fluids. A nut portion 66 on the booster has sufiicient clearance withbore '59 to permit engagement of the nut 'by a wrench. The lower. end ofbooster 62 is provided with a reduced diameter section about which thesheathing 26a of the primer cord. 20 is received. A plurality of annularribs 68 prevent the sheathing from being accidentally removed from theportion 67 of the booster and provide a fluid tight seal therebetween.This depending portion 67 of the booster is provided with a bore'69 inwhich there is received one end of primer .cord 20. Bore 69 terminatesin an imperforate web 76 which prevents the primer cord 21) from beingpushed into the booster-by well fluid.

The powder chamber of the booster is provided by a bore 71 which extendsaway from theweb 7t; and a counter bore 72 which extends the remaininglength of the booster. The booster is loaded by pouring powderedexplosive into its open end to provide a layer of explosive above web70. A pasteboard washer 72 of substantially the'same diameter as bore 71is placed on the powder and supports a blasting cap 73. The blasting capis of slightly lesser diameter than bore '71 and the annular spacebetween the bore and blastingcap is partially filled with powderedexplosive. A rubber washer 74 is then inserted in this annular spaceabove the explosive and a cardboard disk 75 seats against the shoulderbetween bores 71 and 72 and closes the powder chamber.

In using the modified form of fitting, go-devil 21 strikes stop 57 andin the manner explained above sets oif shaped charge 32. Shaped charge32 burns through the imperforate stop 57 and into booster 62 where itboth ignites the loose powder and sets off blasting cap 73. Theseexplosives destroy the thin web 70 and ignite primer cord 20 which inturn ignites the shaped charge in carrier 18. While the force jet ofshaped charge 32 first burns through stop 57 and then ignites the primercord, it will be understood that the speed of the jet is such that forpractical purposes it may be considered that the go-devil simultaneouslypenetrates the stop and fires the primer cord. The subsequent firing ofthe shaped charge 26 also occurs so quickly they may be considered tofire simultaneously with the penetration of the stop. In Figs. 11 and 12there is shown a fitting 55 which formed a part of a gun which has beenfired. It will be noted in Fig. 12 that a substantially centrallylocated hole has been burned through web 57.

Fig. 11 also illustrates the manner in which collar lo cator 17 isutilized to locate the gun opposite a formation where the upper level ofthe formation does not commence immediately below a collar. As it willbe well understood by those skilled in the art, the tubing is run intothe well until the collar locator is below the collar which is desiredto locate. Then the tubing is lifted up until the collar locator fingersengage the collar and impede further upward movement of the tubing. Thetubing is then lowered the desired distance to locate the gun oppositethe formation as illustrated in this figure.

Fig. 13 illustrates the use of a fitting fabricated from a brittlematerial such as cast iron to secure the carrier 18 to the tubing string16. This form of fitting may advantageously be used when running a drystring of tubing to permit reducing the pressure in the well bore whenthe perforating gun is fired. This form of fitting is also preferred forpermanent completion work as it shatters when the go-devil is fired andleaves the bottom of the string of tubing full open to permit work-overoperations at a later date. The fitting may be imperforate or providedwith wash holes depending upon the intended use. Whether the fitting isprovided with wash holes or not, it is preferred that it either have abore section in which the shaped charge of the go-devil is exploded oran internal explosive charge such as the booster in the downrwardlyfacing bore of fitting 55. In either case, there will be a radiallyoutwardly directed force wave from the explosive which will shatter thebrittle fitting. The use of both expedients will provide a safety factorwhen such is desired. When a cast iron fitting is used the collarlocator should be positioned further up the tubing 16 so that it will beabove a joint in the tubing and be retained on the tubing.

It will be understood that either fitting 19 or 55 may be utilizedwithout the circulating ports when it is desired to run the tubing intothe hole dry. In such case, it may be desirable to load the tubing witha column of liquid such as water to prevent the tubing from collapsingdue to the pressure encountered within the well. Of course, the heavymud cannot be removed from the well when the tubing is run dry.

From the foregoing, it is believed that the method of assembly and ofuse of the perforating gun is apparent. The charge carrier 18 may beloaded in the shop or in the field. An entire gun may be loaded andassembled as a unit or the several sections of the carrier 18 may beloaded and taken into the field as sections where they are pinnedtogether by bolts and nuts 25. In either event,

the primer cord 20 is extended from charge to charge and has a portionof its length positioned directly below the stop part of the fittingeither by wrapping the cord about the uppermost shaped charge asillustrated in Fig. 3, or by providing a booster as a part of the primercord as shown in Fig. 14. The charge carrier 18 is made up on eitherfitting 19 or 55 or upon an imperforate form of fitting 19 or 55, as thecase may be, which in turn is secured to the bottom of the string ofproduction tubing to be run into the well. The tubing is run into thewell in the usual manner and the carrier 18 positioned opposite theformation to be perforated, utilizing collar locator 17 in the usualmanner. is employed, the liquid in the well may be replaced by U-tubingif desired. At this time the packer between the tubing and casing isset, all well head connections completed, and the well made ready fornormal production. As there is no heat sensitive explosive in the wellat this time, the time element between location of the carrier in thewell and firing of the gun is not critical, enabling the carrier to berun on the production tubing 16.

The go-devil is loaded either in the shop or in the field as desired. Itwill be noted that the housing 34 may be turned upside down and spring50 dropped into the housing until its large diameter portion Stla restsupon a shoulder provided by bores 35 and 36. Member 41 with itsassociate rim-fire cartridges and shaped charge 32 may be inserted intobore 36 and nose plug 38 screwed into place to hold the assembly inplace. If the housing is maintained in an upright manner so as toprevent dislodging blank cartridges 44, the thus assembled portion ofthe firing mechanism may be handled without danger of accidental firingas hammer 33 is not in place. If desired, the housing may be made up onthe remainder of the go-devil to prevent accidental dropping of anyobjects into bore 35 which might possibly fire one of cartridges 44.When it is desired to drop the go-devil into the well, hammer 33 may beinserted in bore 35 and housing 34 made up on the remainder of thego-devil.

The go-devil may then be inserted through the bull plug in the top ofthe Christmas tree or its equivalent and dropped through the tubinguntil its fall is abruptly arrested by striking the stop part which willactuate the inertia operated hammer 33 causing it to fire blankcartridges 44, which in turn will set off shaped charge 32. The shapedcharge 32 will in turn perforate the fitting and fire the primer cordsetting off the charges in the perforating gun. While the go-devil isfalling through the tubing, the bull plug is replaced in the Christmastree.

Where the tubing is run with a perforate section 16a,

the formation fluid will enter the well in the normal manner assumingthe formation pressure to be greater than the pressure in the well boreat the formation. If this condition does not exist, the column of liquidin the well bore may be lowered by swabbing or the like to permit flowinto the well bore.

Where the tubing is run dry, the pressure in the well bore adjacent theformation at the inistant of firing of the perforating gun will beconsiderably less than the formation pressure and formation fluids willimmediately flow into the well bore.

In Fig. 10 there is shown diagrammatically an improved method of loadingthe primer cord 29 into the protective sheathing 29a. The primer cord isintroduced into the sheathing 20:: by utilizing a T-fitting which hasone of its ports 76 connected to a source of compressed air. Axial port77 of T-fitting 75, through which the cord 2th is inserted, .has aninner diameter which is substantially the same as the outer diameter ofprimer cord 20 to prevent substantial loss of pressure through thisport. Sheathing 20a is first lubricated with soap stone or the like andone end is slipped over port 78 of T-fitting 75. Compressed air is thenintroduced through port 76 and the core of primer cord 20 introducedthrough port 77. Due to the substantial closing of port 77 by primercord 20, the compressed air will fiow out port 78 If a perforate section16a of tubing anon-gee and through sheathing 20a. As the core ofthe'primer cord is" introduced into sheathing 26a, the compressed aitfwill flow between the core and sheathing distending the flexiblesheathing slightly and reducing friction between these two elements sothat the core may be pushed through the sheathing 243:: by loading itthrough port 77. It has been found that primer cords in excess of 100feet in length may be loaded into flexible sheathing using this method.7

From the above it will be seen that the objects set forth have beenaccomplished. There has been provided a method and apparatus forbringing in wells without contaminating the formation, even though theformation pressure be small. There has been provided a means of firingaperforating gun in which the firing mechanism ismaintained separatefrom the remainder of the gun until it is desired to perforate the well.All heat sens-itive powder is contained within the go-devil whichremains in the well only a short time before the. gun is fired and thusthe well temperatures will not afiect the perforating gun. When usingthe invention disclosed, the well. head fittings may be finallycompleted for normal production of the well.

It will be appreciated that while this disclosure hasbeen. principallydirected to a go-devil actuator which is dropped into the well, theactuator might, if desired, be lowered into the well and positioneddirectly over a portion of the primer cord and fired in other ways, aswill be understood by those skilled in the art. While this wouldaccomplish the desired results, the structure would be more complicatedand would present hazards not present with the go-de-vil type ofactuator.

From the foregoing it will be seen that this invention is one welladapted to attain all of the ends and objects hereinabove set forth,together with other advantages which are obvious and which are inherentto the method and apparatus.

Itv will be understood that certain features and sub combinations are ofutility and may be employed with out reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth. or shown inthe accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

The invention having been described, what. is claimed is:

1. The method of perforating a well comprising, lowering a loadedperforating gun, with a primer cord for firing it, into a well andpositioning the gun at the desired depth, then lowering an explosivecharge until. the charge is positioned adjacent a portion of the primercord which forms a part of the perforating gun and which when ignitedwill fire the gun, and setting off the explosive charge to ignite theprimer cord.

2. A perforating gun for wells, comprising, a carrier having securingmeans adapted to be secured to the bottom of a string of tubing, a stoppart adjacentv the top of the carrier and positioned to block thepassage of a body entering the carrier through said securing means, aprimer cord, which when ignited will fire the perforating gun, extendingalong said carrier and having a portion of its length positioneddirectly below the stop part and a portion positioned to fire the gunwhen the cord is ignited, and an actuator comprising a body adapted tobe lowered into the carrier through said securing means until. theactuator reaches the stop part, a downwardly firing charge in the noseof said body and means for firing said charge, whereby the primer cordwill be ignited by the charge when the actuator is fired while adjacentthe stop part.

3. .A perforating gun for wells, comprising, a carrier having securingmeans adapted to be secured to the bottom of a" stringof tubing, a stoppart adjacent the top of the carrier and positioned toblock the passageof a body entering the carrier through said securing means, a primercord, which when ignited will fire the perforating gun, extending alongsaid' carrier and having a portion of its length positioneddirectlybelow the stop part and a portion positioned to fire the gun when thecord is ignited, a go-devil actuator comprising a body adapted to bedropped into the carrier through said securing means and strike the stoppart, a downwardly firing charge in the nose of the body, and meansresponsive to the actuator striking the stop part for firing said chargetov ignite theprimer cord.

4 A perforating gun for wells, comprising, a carrier havingsecuringmeans adapted to be secured to the bottomof a string of tubing, 2. stoppart adjacent the top of the carrier and positioned to block the passageof a body entering the carrier through said securing means, a primercord, which when ignited will fire the perforating gun, extending alongsaid carrier and having a portion of its length positioned directlybelow the stop part and a portion positioned to fire the gun when thecord is ignited, and a go-devil actuator comprising a body adapted to bedropped into the carrier through said securing means and strike the stoppart, a downwardly firing charge on the nose of said body, and aninertia operated firing mechanism operable to set off said. charge when.the actuator strikes the stop part, whereby the primer cord will beignited when the actuator charge is fired by striking of the actuatoragainst the stop part;

5. The gun of claim 4, wherein the securing means is a fitting forsecuring the gun to the string of tubing and the stop part is providedby said fitting.

6. The gun of claim 5, wherein the fitting is provided with an inwardlyand downwardly tapered bore above the stop part which centers theactuator in the fitting to aim the blast from the charge.

7. The gun of claim 6, wherein the stop part is an imperforate,transverse member which closes said bore, said portion of the primercord is positioned directly below the transverse member, and the chargeis a shaped charge which when fired penetrates the transverse member andignites the primer cord.

8. The gun of claim 6, wherein the stop part is an imperforate,transverse member which closes said bore, said portion of the primercord is a booster positioned in the fitting directly below thetransverse member, and the charge is a shaped charge which when firedpenetrates the transverse member and ignites the booster.

9. A perforating gun for wells, comprising, a carrier having securingmeans adapted to be secured to the bottom of a string of tubing, astoppart adjacent the upper. section of the carrier and positioned to blockthe pas- I sage of a body entering the carrier through said securingmeans, a primer cord, which when ignited will fire the perforating gun,extending along said carrier and having a portion of its lengthpositioned directly below the stop partand a portion positioned to firethe gun when the cord is ignited, and an actuator comprising a bodyadapted to be dropped into the carrier through said securing means untilits fall isv abruptly arrested by the stop part, a downwardly directedexplosive charge on said body, and a firing mechanism for said explosivecharge includ ing a spring-loaded, inertia-operated hammer, and a blankcartridge under the hammer which when fired will. set off the explosivecharge, whereby the primer, cord will be ignited by said explosivecharge when the firing. mechanism is operated by the actuator strikingthe stop.

10. A fitting for securing to a string of tubing a perforating gun ofthe type employing an actuator which is separate from the remainder ofthe gun, comprising, a tubular body having a bore in one end, means onthe body for connecting said end to a spring of tubing and the oppositeend to a gun, said bore provided with an in wardly tapering section andan imperforate transverse wall extending across said bore adjacent thesmall diameter portion of the tapering section.

11. The fitting of claim 10, wherein the fitting is brittle and willshatter into fragments when a shaped charge is set off in said bore.

12. A fitting for securing to a string of tubing a perforating gun ofthe type employing a go-devil actuator which fires upon impact,comprising, a tubular body having a bore in its end adapted to besecured to the string of tubing, said bore having an inwardly taperingsection and a transverse wall extending across and closing the bore adjacent the small diameter portion of the tapering section to provide acentering means and a stop, respectively, for a go-devil, and acirculation port extending between the exterior of the body and saidbore adjacent the wall.

13. An actuator for use in wells, comprising, a godevil having anexplosive charge in its nose, positioned to fire outwardly of thego-devil, and an inertia operated firing mechanism including an inertiaoperated hammer carried by the actuator for setting off the charge.

14. An actuator for use in wells, comprising, a go-devil with anexplosive charge in its nose, and a firing mechanism carried by theactuator for setting off the charge including an abutment wall, aninertia operated springloaded hammer above the wall and a blankcartridge and firing pin under the hammer and positioned to be engagedupon descent of the hammer to set off the charge.

15. A go-devil actuator, comprising, an elongate, tubular body having aslide chamber extending axially of the body and terminating in abutmentwalls, an explosive charge in the nose of the body, a blank cartridge inone abutment wall of said chamber adjacent the charge which when firedwill set off the charge, a hammer slidable in said chamber to strike andfire the cartridge, and resilient means urging the hammer away from thecartridge.

16. A go-devil actuator, comprising, an elongate, tubular body having aslide chamber extending axially of the body and terminating in abutmentwalls, an explosive charge in the nose of the body, a blank cartridge inone abutment wall of said chamber adjacent the charge which when firedwill set off the charge, a hammer slidable in said chamber to strike andfire the cartridge, a resilient means urging the hammer away from thecartridge and against the other abutment wall of the chamber, and ablank cartridge in one of the opposed surfaces of said hammer and otherabutment wall, and a firing pin on the other such surface which whenfired by the hammer moving away from said other wall and being returnedby the spring will drive the hammer against said first-mentionedcartridge with sufiicient force to fire said first-mentioned cartridge.

17. In combination, a fitting for closing the lower end of a string oftubing adapted to be run into a well, said fitting having a bore in itsend adapted to be secured to the string of tubing and fabricated of abrittle material which will shatter when an explosive is set off in saidbore, and an actuator comprising, an elongate, tubular body having anexplosive charge in its nose and means for setting off said charge, saidcharge when exploded in said bore shattering the fitting into fragments.

18. In combination, a fitting for closing the lower end of a string oftubing adapted to be run into a well, said fitting having a bore in itsend adapted to be secured to the string of tubing and fabricated of abrittle material which will shatter when an explosive is set off in saidbore, a perforating gun depending from the fitting, and an actuatorcomprising, an elongate, tubular body having an explosive charge in itsnose and means for setting off said charge, said charge when exploded insaid bore simultaneously shattering the fitting into fragments andfiring said perforating gun.

19. In combination, a fitting for closing the lower end of a string oftubing adapted to be run into a well, said fitting fabricated of abrittle material which will shatter when subjected to an explosion fromwithin and having a bore in its end adapted to be secured to a string oftubing, an explosive charge positioned in said fitting, and an actuatorcomprising, an elongate, tubular body having an explosive in its nose,and means for setting off the charge in the actuator, said actuatedcharge in turn setting otf the explosive charge in the fitting, said twoex:

plosive charges shattering the fitting into fragments.

20. The combination of claim 19 wherein the charge in the fitting is apart of a perforating gun which is fired by setting off said charge inthe fitting.

21. The method of completing a well, comprising, running a perforatinggun into a cased well bore on a string of tubing closed to entry offluid from the well bore and positioning the gun opposite the formationto be produced, setting a packer between the casing and tubing above theformation to be produced to pack off the formation from fluid in theannular space between the casing and tubing and above the packer, andcompleting the well by simultaneously opening said tubing to fluid belowthe packer and firing the perforating gun, whereby when the formation tobe produced is perforated the weight of the column of fluid in theannulus between the casing and tubing and above the packer will not beexerted on the formation.

22. In combination, a string of tubing adapted to be lowered into awell, a fitting closing the lower end of said string of tubing to entryof fluids, and a go-devil actuator for perforating said fitting andopening the string of tubing to fluids, and go-devil actuatorcomprising, an elongate, tubular body, an axially firing shaped chargein the nose of the body, and a firing mechanism carried by said body forsetting off the shaped charge when the godevil lands upon the fitting.

References Cited in the file of this patent UNITED STATES PATENTS1,461,130 Loughead July 10, 1923 2,023,831 Ellis Dec. 10, 1935 2,313,369Spencer Mar. 9, 1943 2,362,829 Kinley Nov. 14, 1944 2,530,844 Tow Nov.21, 1950 2,530,966 Huber Nov. 21, 1950 2,545,504 Villafane Mar. 20, 19512,586,911 Bottom Feb. 26, 1952 2,627,160 MacDonald Feb. 3, 19532,629,325 Sweetman Feb. 24, 1953 1,645,004 Dorner July 14, 19532,679,899 Osborn June 1, 1954 2,681,110 Harrison June 15, 1954 2,725,820McCullough Dec. 6, 1955 2,733,657 Bryant et al. Feb. 7, 1956 2,740,477Monaghan Apr. 3, 1956 No. 2,906,339, W.

H. Griffin, udgment adverse to the d 2.

Notice of Adverse Decision in Interference In Interference N 0. 92,204:involving Patent No. 2,906,339, WV. H. Griflin, Method and apparatus forcompleting Wells, final judgment adverse to the patentee Was renderedFeb. 12, 1963, as to claims 1 and 2.

[Ofii'oial Gazette Apm'l 30, 1963.]

